Barrikaide, you're a solid hitter. 1/2" sch 40 PVC is probably not going to stand up very well for you, although on a flail it may last longer. I would expect it to flex out when the core is somewhere around 28-30". The chain needs to be 6" or less, the head must have a circumference of 16" or more and the head must weigh at least 4oz. I usually make flails to be about 36-40" overall.
As far as padding, I usually put 2 layers of walmart blue for the last 12 inches of the flail handle (closest to the 'chain') and then do the remaining courtesy padding at one layer. Pool noodle breaks down pretty fast, skip it.